net/mlx5: Increase number of ethtool steering priorities

Ethtool has 11 flow tables, each flow table has its own priority.
Increase the number of priorities to be aligned with the number of flow
tables.

Fixes: 1174fce8 ('net/mlx5e: Support l3/l4 flow type specs in ethtool flow steering')
Signed-off-by: Maor Gottlieb <maorg@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>